The present invention relates to vaginal rings.
Vaginal rings composed of synthetic resins, and containing active ingredients, have been known for some time. DOS No. 2,450,107 and its U.S. equivalent 4,012,496 describe a vaginal ring consisting of a supporting ring with one or two continuous pocket-like indentations adapted to accommodate active-agent-containing rings which fit into these indentations and are made of a synthetic LTV silicone elastomer resin.
U.S. Pat. No. 3,920,805 likewise describes a vaginal ring of a silicone elastomer consisting of a core free of active agent and a coating containing an active agent.
Both systems have in common that the active ingredient is released directly to the surrounding body parts from the part containing the active agent.
However, annular devices are likewise conventional wherein the part containing the active agent is coated with a diaphragm free of active ingredient (U.S. Pat. No. 3,854,480). In this device, the annular core consists of a silicone elastomer containing an active agent, encompassed by a polyethylene hose having a wall thickness of about 0.8 mm.
The conventional vaginal rings, however, are disadvantageous in that the release rate over the desired time period is not constant. Rather, the amount per unit time becomes increasingly smaller after an initial surge of active agent.